Disclosed in the present invention is an application of EphrinA1 in development, progression, metastasis, and treatment of tumors and survival prognosis of patients. Disclosed in the present application is that EphrinA1 is involved in growth, invasion and metastasis processes of tumors; the high expression of EphrinA1 in gastric cancer tissues leads to poor prognosis of gastric cancer patients, and targeted knockdown or knockout of the expression of EphrinA1 can significantly inhibit the invasion ability of gastric cancer cells and the metastasis ability in mice. The present invention can effectively inhibit the invasion ability of gastric cancer cells by blocking the function of EphrinA1 by using an antibody targeting EphrinA1. According to the present invention, it is found that EphrinA1 has an important application value in tumor therapy and can be used as a target for antitumor drugs.